Interpretive Summary: Many accessions of the USDA peanut germplasm collection are heterogeneous. Using homogeneous accessions is critical for many types of phenotypic and genomic evaluations. The objectives of this research were to purify accessions of the USDA mini-core collection and characterize genetic variation of this collection using morphological and chemical traits, and molecular markers. Twenty seeds of one hundred and four accessions of the peanut mini-core collection were planted at Dawson, GA in 2008 under irrigated conditions. The seeds from five uniform plants were harvested, bulked, and planted in Headland, AL in 2009 to continue the purification process. In 2010, homogenous seeds of each accession were planted in Headland, AL to increase seed counts for chemical analysis and genotyping. Phenotyping was evaluated for agronomic traits, pod and seed traits, seed dormancy, and seed quality traits including oil content, fatty acid composition, and flavonoids for two years. Significant variability was detected in seed chemical composition among accessions and botanical varieties. Accessions with high amounts of oil, quercetin, high seed weight, and O/L ratio were identified. Significant variability in seed dormancy was observed among accessions and botanical varieties. Indel markers revealed that among four existing botanical varieties in the collection peruviana var. has a higher level of diversity than fastigiata var., hypogaea var, and vulgaris var., but they are lower than aequatoriana var. and hirsuta var. It is recommended that accessions from aequatoriana var. and hirsuta var should be added to the U.S. mini-core collection and used in peanut breeding programs.

Technical Abstract:
Many accessions of the USDA peanut germplasm collection are heterogeneous. Advances in genomics technology have highlighted the need for collections of homogeneous accessions. Using homogeneous accessions is critical for many types of phenotypic and genomic evaluations. The objectives of this research were to purify accessions of the USDA mini-core collection and characterize genetic variation of this collection using morphological and chemical traits, and molecular markers. Twenty seeds of one hundred and four accessions of the peanut mini-core collection were planted at Dawson, GA in 2008 under irrigated conditions. The seeds from five uniform plants were harvested, bulked, and planted in Headland, AL in 2009 to continue the purification process. In 2010, homogenous seeds of each accession were planted in Headland, AL to increase seed counts for chemical analysis and genotyping. Phenotyping was evaluated for agronomic traits, pod and seed traits, seed dormancy, and seed quality traits including oil content, fatty acid composition, and flavonoids for two years. Significant variability was detected in seed chemical composition among accessions and botanical varieties. Accessions with high amounts of oil, quercetin, high seed weight, and O/L ratio were identified. Significant variability in seed dormancy was observed among accessions and botanical varieties. Indel markers revealed that among four existing botanical varieties in the collection peruviana var. has a higher level of diversity than fastigiata var., hypogaea var, and vulgaris var., but they are lower than aequatoriana var. and hirsuta var. It is recommended that accessions from aequatoriana var. and hirsuta var should be added to the U.S. mini-core collection and used in peanut breeding programs.